Starter drive with positive advance and inertia release

ABSTRACT

A STARTER DRIVE HAVING POSITION RESPONSIVE ADVANCE ASSIST MEANS CAPABLE OF PREVENTING DISENGAGEMENT OF THE DRIVE IN THE EVENT OF A FALSE START. THE ASSIST MEANS COMPRISE, IN THE PREFERED EMBODIMENT, AN AXIALLY-MOVABLE ELECTROMAGNETIC BRAKE WITH A NON-ROTATING COIL AND MAGNET BODY. AS THE DRIVE ADVANCES, AN ELECTRICAL CONTACT FOR THE COIL SLIDES ALONG A CONDUCTING STRIP WHICH TERMINATES IMMEDIATELY BEFORE THE DRIVE REACHES ITS FULLY ADVANCED POSITION DE-ENERGIZING THE BRAKE AND THEREBY RELEASING THE ADVANCE ASSIST.   D R A W I N G

Min]! 23, 19.71 P. F. GIOMETTI ,57 ,1

STARTER DRIVE WITH POSITIVE ADVANCE AND INER'IIA RELEASE Filed April 4, 1969 IN VENTOR.

WITNESS ATTORNEY United States Patent Ofice 3,572,133 Patented Mar. 23, 1971 3,572,133 STARTER DRIVE WITH POSITIVE ADVANCE AND INERTIA RELEASE Paul F. Giometti, Horseheads, N.Y., assignor to The Bendix Corporation Filed Apr. 4, 1969, Ser. No. 813,455 Int. Cl. F0211 11/00 US. Cl. 74-7 Claims ABSTRACT OF THE DISCLOSURE A starter drive having position responsive advance assist means capable of preventing disengagement of the drive in the event of a false start. The assist means comprise, in the preferred embodiment, an axially-movable electromagnetic brake with a non-rotating coil and magnet body. As the drive advances, an electrical contact for the coil slides along a conducting strip which terminates immediately before the drive reaches its fully advanced position de-energizing the brake and thereby releasing the advance assist.

CROSS-REFERENCE This disclosure is relates to the commonly assigned, copending applications Ser. No. 680,258 Starter Drive With Selectively Releasable Friction Advance by James E. Buxton, et al., now United States Letters Patent, 3,465,353 and Ser. No. 734,998 Starter Drive With Friction Advance and Inertia Release by James E. Buxton, now United States Letters Patent 3,496,759.

SUMMARY OF THE INVENTION The present invention relates to starter drives for internal combustion engines. It is known that a pinion of a starter drive may be advanced into engagement with the ring gear of an engine to be started by mounting the drive on a helical screw shaft and rotating the shaft at a faster rotational Velocity than the drive is rotated. It is also 'known that the rotation of the drive can be impeded by applying a retarding force in the form of rotational friction. When the frictional force is sufiicient for axially shifting the drive into engagement and preventing inadvertent disengagement, the frictional force can consume as much as 10% of the total power of the starting motor during cranking. It is, therefore, an object of this invenntion to provide a starter drive having an advance assist means which does not consume starter power to any significant degree during cranking, but which provides suflicient assist to advance the drive into engagement and prevent inadvertent disengagement. It is also an object of this invention to provide a position responsive selective assist means for a starter drive. It is a still further object of my invention to provide an electromagnetic brake means as an advance assist for a starter drive to selectively povide position sensitive pinion advance assist which does not rob starter motor torque during cranking.

The inventions disclosed and claimed in the referenced patent applications relied upon the available reactive thrust developed by abutment of the rotary drive portion with the starter drive housing, When fully engaged, to cause a friction disk pack to separate and thereby term nate the power consuming friction connection between the shiftable drive portion and the starter drive housing. This requires some rather close tolerances as well as expensive assembly techniques. It is, therefore, a still further object of this invention to provide a means having a friction connection between the shiftable drive portion and the starter drive housing for assisting the advance of the shiftable drive portion into engagement with the ring gear of an engine to be started which does not rely upon reactive thrust to terminate the friction connection and is lower in cost and easier to assemble than known drives of this type. Specially, and in light of the above objective, it is an object of this invention to provide electric position sensitive means responsive to the axial travel of the shiftable drive portion to terminate the connection between the shiftable drive portion and the starter drive housing when the pinion has partially engaged the ring gear Whereby screw jack action can complete the engagement.

In the preferred embodiment of my invention, I employ a shiftable, non-rotatable electromagnetic brake, having a sliding electrical contact, to interconnect the shiftable drive portion and the starter housing to prevent drive rotation and facilitate drive advance. As the drive advances toward full engagement with the ring gear of an engine to be started, the sliding electrical contact moves off of an energized conducting strip permitting the brake to be de-energized thereby freeing the drive for rotation. It is believed that the braking forces are sufficient to prevent pinion rotation thereby gaining the advantages of the solenoid type of positive shift starter drive without requiring the power consuming solenoid to maintain the drive in engagement.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing shows a side view of a starter drive according to my invention, partly in section, in the de-energized position.

DETAILED DESCRIPTION Referring now to the drawing, a starter drive is shown which represents a preferred embodiment of my invention. The shiftable drive portion, indicated generally by 10, is mounted in co-operative association with the helical screw shaft of the starter motor, not shown. The shiftable drive portion 10 is comprised of a screw shaft sleeve 16 co-operatively engaging the screw shaft 12, the advance assist means 20, a unidirectional clutch means 22, the pinion 24 and the starter drive housing 26. The shaft sleeve 16 is connected to the outer race 28 0f the clutch means 22 while the inner race 30 of the clutch means 22 is connected to the pinion 24 thus providing a unidirectional torque transmitting connection between the output shaft 12 of the starter motor, no shown, and the pinion 24. The sleeve 16 and outer race 28 comprise the starter drive body.

Without a load or drag on the pinion 24, rotation of the screw shaft 12 would cause concomitant rotation of the shiftable drive portion 10 and of the pinion 2 4. It is, therefore, necessary to prevent the shaft sleeve 16 from rotating with the screw shaft 12 so as to cause the shaft sleeve 16 to axially traverse on the shaft 12 to bring the pinion 24 into engagement with the ring gear 32 of an engine to be started, not shown. The advance assist means 20 is operative to cause the desired axial translation of the pinion.

The advance assist means is comprised of an electromagnetic brake means including a stationary magnet body 34, an electromagnetic coil means 36, an armature means 38 and current conducting means 40. The magnet body 34 is slidingly connected to the starter drive housing 26 through flange 42 which slides in a slot 44 in the insulating block 54. The current conducting means 40 is comprised of resilient contact member 48 and suitably insulated lead 50 which connects the resilient contact member 48 to the coil means 36.

The starter drive housing 26 includes a conducting strip 52 which is imbedded within insulated block 54 and is, therefore, insulated from the starter drive housing 26. The resilient contact member 48 is in sliding contactive engagement with the conducting strip 52 for most of the axial travel distance of the shiftable drive portion 10.

Upon energization of the starter motor in the conventional manner, conducting strip 52 is also energized causing current to flow in the coil means 36. This produces an electromagnetic flux in the magnet body 34 and the armature means 38. Instead of being a separate member attached to clutch means 22, the armature means 38 could be eliminated and the clutch means 22 could include an armature portion. Because the magnet body is prevented from rotating and is clamped by electromagnetic force into contact with the armature means 38, the shaft sleeve 16, the clutch means 22 and the pinion 24 are prevented from rotating with the shaft 12, but are caused to axially translate on the shaft until the pinion 24- engages the ring gear 32.

At some predetermined point where pinion teeth and ring gear teeth overlap, but prior to full engagement, the sliding contact member 48 will slide off the energized conducting strip 52 and the coil means 36 will be deenergized releasing the rotational retarding force on the armature means 38. As the pinion 24 attempts to rotate, contact between the pinion 24 and ring gear 32 provides the drag or loading required to complete the engagement. This drag will also advance the armature 38 away from the magnet body 34 so contact and wear therebetween is prevented.

If, during engine cranking, compression peaks or false firing of the engine induces a momentary overspeed of the ring gear 32 relative to the p nion 24, i.e. the clutch means 22 overruns, the strong engagement forces due to transmitted torque are released. In many prior devices, this presented the possibility of premature disengagement. Should such a condition occur with the present device and the pinion 24 begins to retract from ring gear 32, the resilient contact member 48 will re-contact the current conducting strip 52 and, because the starter motor and current conducting strip 52 are still energized, the starter drive will be forced to remain in engagement.

Upon self-sustaining engine operation, the operator will terminate the start-up cycle by de-energizing the starting motor. The conducting strip 52, which can either be in series or in parallel with the starting motor, will be in the preferred embodiment of my invention, in series with operator controlled starting switch so that when the starting motor is de-energized, the current conducting strip 52 will be concomitantly de-energized. This permits the electromagnetically initiated friction connection of the advance assist means to be terminated and inertia forces generated by the decelerating starter motor and operating on the starter drive will disengage the drive 10 from ring gear 32.

In the event that the pinion 24 advances into an abutting condition with the ring gear 32, the advance of the drive will be impeded and rotation of the shaft 12 will cause slipping between the magnet body 34 and the armature means 38 and will, therefore, cause limited rotation of the pinion 24. This will terminate the abutment thereby allowing the engagement to proceed.

The starter drive, as shown, accomplishes its stated objectives in providing an advance assist for a starter drive which is position sensitive and capable of ignoring false starts.

I claim:

1. A starter drive for internal combustion engines having a starter drive housing, a motor driven shaft means having a helical screw thread thereon, and a shiftable drive portion, the shiftable drive portion comprising:

a screw sleeve means for cooperatively engaging sa d shaft means;

a drive pinion means;

a unidirectional clutch means interconnecting said sleeve means and said pinion means; and

advance assist means interconnecting the starter drive housing and the shiftable drive portion operative to provide a position sensitive rotational braking force so that rotation of said sleeve means is selectively braked to cause the helical screw thread to advance said pinion means into engagement with the engine whenever the extent of the advance of the shiftable drive portion on the shaft means is less than a pre determined amount.

2. The starter drive as claimed in claim 1 wherein said advance assist means comprise electromagnetic brake means slidingly interconnecting said starter drive housing and said sleeve means.

3. The starter drive as claimed in claim 2 including further:

a conducting means connected to, and insulated from,

said housing; and

resilient current conducting contact means attached to said electromagnetic brake means and in sliding contact with said conducting means operative to provide a current conducting path from said conducting means to said electromagnetic brake means.

4. The starter drive as claimed in claim 3 wherein said conducting means are arranged to terminate the current conducting path prior to full engagement of said drive pinion means with the engine to be started.

5. The starter drive as claimed in claim 1 wherein said advance assist means comprise:

a magnet body slidingly coupled to said housing:

a coil means fixedly connected to said magnet body;

an armature means connected to said shiftable drive portion; and the housing includes current conducting means operative to provide said coil means with electrical energy.

6. The starter drive as claimed in claim 5 wherein said current conducting means comprise:

a source of electrical energy;

a conducting strip means attached to and insulated from said housing; and said advance assist means include a resilient contact member connected to said coil means and in sliding contact with said conducting strip means.

7. The starter drive as claimed in claim 1 including further:

electric advance assist means connected to the housing operative to determine the position to which said advance assist means is sensitive.

8. The starter drive as claimed in claim 7 wherein:

said electric advance assist means comprise conducting means having a predetermined length; and

sliding contact means adapted to contactively engage said conducting means and operative to axially ad- Vance with the shiftable drive portion whereby electrical contact between said conducting means and said sliding contact means is terminated when the shiftable drive portion advances beyond the desired position.

9. The starter drive as claimed in claim 8 wherein said conducting means are embedded in, and suitably insulated from the starter drive housing.

10. A shiftable drive of a starter system for internal combustion engines having a starter drive housing, a motor, a motor driven shaft means having a helical screw thread thereon comprising:

a screw shaft sleeve means for cooperatively engaging References Cited the shaft means; a drive pinion means; UNITED STATES PATENTS a one-way clutch means interconnecting said sleeve 1,897,938 2/1933 Kearney 74-7 meansandsaid pinion n w 2,332,986 10/1943 Buxton 74 7 electromechanical means for selectively, slidably and 5 I nonrotatably interconnecting the shiftable drive With MILTON K AUFM AN Primary Examiner the housing, responsive to energization of the motor to provide rotational braking of the shiftable drive 1 portion whenever the motor is energized and the 29O 38 shiftable drive portion is advanced less than a prede- 10 termined amount. 

